JPH08145950A - Mass spectrometer - Google Patents

Abstract

PURPOSE: To improve the separating capacity of mixed samples in a liquid chromatograph mass spectrometer by using moving phase solvent containing volatile retardant salt. CONSTITUTION: The sample separated by a liquid chromatograph 14 is sprayed by an electrostatic sprayer 15, and thermally vaporized by a vaporizer 5. The obtained gaseous sample molecules are ionized by a proton addition reaction, etc., by chemical reaction by an ionizer 6 having a corona discharger, introduced from ion introducing pores 9a, 9b into a high vacuum unit 12, and analyzed by a mass spectrometric analysis part 13. The salt contained in the solution is converted gaseous ions, bent at its orbit by the electric field near the pores, and hence the blocking of the pores by the precipitation of volatile retardant salt can be prevented.

Description

Detailed Description of the Invention

[0001]

The present invention relates to sugars and peptides,
The present invention relates to a device, which is used for separation and analysis of a mixed sample related to a living body such as a protein, in which a liquid chromatograph and a mass spectrometer are combined, that is, a liquid chromatograph / mass spectrometer.

[0002]

2. Description of the Related Art At present, in the field of analysis, development of mass spectrometry for bio-related substances is emphasized. Since bio-related substances are usually dissolved in a solution as a mixture, development of a device for connecting a means for separating the mixture and a mass spectrometer is under way. A typical apparatus for this method is a liquid chromatograph / mass spectrometer (hereinafter abbreviated as LC / MS). A liquid chromatograph (hereinafter abbreviated as LC) is excellent in separating a mixture but cannot identify a substance, whereas a mass spectrometer (hereinafter abbreviated as MS) is high in sensitivity and excellent in an ability to identify a substance, Analysis is difficult. Therefore, LC / MS, which uses MS as a detector of LC, is very effective for analyzing a mixture.

Referring to FIG. 8, Analytical Chemistry, 1988, 60, 774 [Analytical Che
mistry, 60 , 774 (1988)], LC / MS using the conventional atmospheric pressure chemical ionization method will be described.

The sample solution eluted from the LC is pipe 1,
It is introduced into the metal tube 3 via the connector 2. The metal tube 3 is embedded in the metal block 4a. Metal block 4
The sample solution introduced into the metal tube 3 is sprayed by heating a with a heating means such as a heater. Fine droplets generated by spraying are heated metal blocks 4
It is introduced into the vaporization section 5 constituted by b. Vaporizer 5
The sample molecules vaporized at are introduced into the ionization section 6. The ionization part 6 is provided with a needle electrode 7.
By applying a high voltage of several kV to the needle electrode 7 by the high voltage power source 8a, corona discharge is generated in the ionization section 6.

In the atmospheric pressure chemical ionization method, when A is a sample molecule to be analyzed and B is a molecule of a reaction gas, ions relating to the sample molecule A are mainly produced by the following proton addition reaction or proton desorption reaction. A + BH + → AH ++ B (proton addition reaction) A + B ⁻ → (A−H) ⁻ + BH (proton desorption reaction) Therefore, in the conventional technique shown in FIG. 8, the hydronium ion is generated by causing corona discharge in the atmosphere. (H ₃ O +)
Is generated, and the following reaction between it and the sample molecule A is used to generate the ion AH + for the sample A. In the A + H ₃ O + → AH ++ H ₂ O ionization section 6, the ions relating to the sample generated by the chemical reaction represented by the above-described reaction are differentially exhausted by the ion introduction pore 9a and the exhaust system 10a. Exhaust system 10b through exhaust unit 11 and ion introduction pores 9b
Is introduced into the high vacuum portion 12 that has been evacuated to a high vacuum.
The ions introduced into the vacuum are subjected to mass analysis by the mass spectrometric section 13.

[0006]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention In a detector other than MS, for example, an LC having an ultraviolet absorption detector that detects a sample by a change in the absorbance of ultraviolet rays, in order to improve the separation ability and the reproducibility of the elution time of the sample, In some cases, a mobile phase solvent containing a hardly volatile salt is used. However, when a mobile phase solvent containing a sparingly volatile salt is used for LC / MS, this salt precipitates around the ion-introducing pores for introducing ions from the atmosphere into the vacuum, and the ion-introducing pores are formed. I will block it. Therefore, in LC / MS, it is difficult to use a mobile phase solvent containing a sparingly volatile salt, and it was not possible to perform an analysis that makes full use of the high separation capacity of LC. For this reason, it is less susceptible to the effects of non-volatile salts in the mobile phase solvent,
There is a demand for LC / MS that can fully utilize the high separation capacity of LC.

An object of the present invention is to make it possible to use a mobile phase solvent containing a hardly volatile salt, which was difficult to use in the conventional LC / MS.

[0008]

In the present invention, LC
Atomize the sample solution sent from the
The above-mentioned object is achieved by ionizing a gaseous sample molecule obtained by vaporizing the obtained droplet by a chemical reaction and analyzing the ions relating to this sample molecule by MS.

FIG. 1 is a schematic diagram showing the structure of the LC / MS of the present invention. The sample separated by the LC 14 is sprayed in the electrostatic spraying unit 15 together with the mobile phase solvent. The vaporization of the droplets obtained by the spraying is promoted in the vaporization unit 5. The gaseous sample molecules generated in the vaporization section 5 are ionized by a chemical reaction in the ionization section 6. Ions relating to the sample generated in the ionization unit 6 are the ion introduction pores 9a,
Differential exhaust unit 11 exhausted by the exhaust system, 9b through the ion introduction pores, high vacuum unit 12 exhausted by the exhaust system
Will be introduced to. The ions introduced into the vacuum are subjected to mass analysis by the mass spectrometric section 13.

The ionization section 6 may be provided in the differential pumping section 11. The differential evacuation unit 11 has a pressure of several Pascals to several hundred Pascals, and collision between sample molecules and reaction gas occurs, so that ions can be generated by a chemical reaction. Further, in the vaporizing section 5, a vaporizing means such as a heated metal block or infrared irradiation can be used.

[0011]

[Function] Since the mobile phase solvent sent from the LC is electrostatically sprayed, the salt which is dissociated in the solvent and becomes an ion is converted into a gaseous ion only by spraying. Therefore, the ions derived from the salt are trapped in the metal block that constitutes the vaporization section, or the orbit can be bent by the potential applied to the needle electrode provided in the ionization section,
Cannot reach the ion introduction pores. Therefore, even if a mobile phase solvent containing a sparingly volatile salt is used, the salt does not deposit around the ion-introducing pores, and there is no risk of blocking the ion-introducing pores. For the above reasons, the LC / MS of the present invention can use a mobile phase solvent containing a hardly volatile salt, which has been difficult to use conventionally.

[0012]

FIG. 2 is a diagram showing a more detailed structure of the structure shown in FIG. The sample solution eluted from the LC is introduced into the metal pipe 3 via the pipe 1 and the connector 2. Several kV between the metal tube 3 and the metal block 4b by the high voltage power supply 8b
The sample solution is electrostatically sprayed by applying the voltage. The minute droplets generated by the spraying are introduced into the vaporizing section 5 formed by the heated metal block 4b. The metal block 4b is heated to about 3 by a heater (not shown).
It is heated to about 00 ° C. The droplets generated by the atomization are vaporized by heat while passing through the opening of the metal block 4b.

The sample molecules vaporized in the vaporization section 5 are introduced into the ionization section 6. The ionization part 6 is provided with a needle electrode 7. By applying a high voltage of several kV to the needle electrode 7 by the high voltage power source 8a, the ionization unit 6
Generate a corona discharge. When the gaseous sample molecules obtained by vaporizing the droplets reach the corona discharge portion, they chemically react with primary ions such as hydronium ions generated by the corona discharge, and the ionization of the sample molecules is achieved. At this time, since the refractory salt in the solvent dissociates into ions, it is converted into gaseous ions only by electrostatic spraying.

The ions derived from the salt are trapped by the metal block 4b constituting the vaporization part 5 or the trajectory is bent by the potential applied to the needle electrode 7 provided in the ionization part 6, so that the ion introduction is performed. The pores 9a cannot be reached. Therefore, even if a mobile phase solvent containing a refractory salt is used,
Salt does not precipitate around the ion introduction pores 9a,
There is no possibility of blocking the ion introduction pore 9a. Therefore,
The LC / MS of the present invention can use a mobile phase solvent containing a sparingly volatile salt, which has been difficult to use in the past, and enables LC / MS analysis making full use of the separation ability of LC.

When the flow rate of the solution sent from the LC is large and it is difficult to stably maintain electrostatic spraying, a splitter 16 is provided as shown in FIG. May be introduced into the metal tube 3. Similarly, as shown in FIG. 2, the atomizing gas 1 is supplied from the outside of the metal tube 3.
7 may be flowed to assist the electrostatic spraying.

When the flow rate of the solution sent from the LC is small and it is difficult to stably maintain the electrostatic spray, or when the viscosity and the electric conductivity of the solution are too high, the electrostatic spray can be stably maintained. If it is difficult, as shown in FIG. 2, by spraying the spray auxiliary solution 18 from the outside of the metal tube 3 and mixing with the solution sent from the LC,
The conditions such as the flow rate, viscosity, and electric conductivity may be adjusted to the conditions under which the electrostatic spray can be stably maintained.

The tip of the metal tube 3 may be provided in the vaporizing section 6, as shown in FIG. Alternatively, as shown in FIG. 3, the solution may be directly sprayed toward the metal block 4b. The sample solution is electrostatically sprayed by the high voltage applied from the high voltage power source 8b between the metal tube 3 and the metal block 4b. The insulation between the metal tube 3 and the metal block 4b is performed by the insulating tube 19. The droplets sprayed on the metal block 4b heated to a temperature higher than the boiling point of the solution are instantly vaporized, and gaseous sample molecules are obtained. When the sample molecule reaches the corona discharge part, it causes a chemical reaction with primary ions such as hydronium ions generated by the corona discharge,
Ionization of sample molecules is achieved. Ions related to sample molecules are exhausted to about 10 ⁻³ Pa by the exhaust system 10b through the differential exhaust unit 11 which is exhausted to several tens Pa to several hundred Pa by the ion introduction pore 9a and the exhaust system 10a. It is taken into the unit 12 and subjected to mass analysis by the mass spectrometric unit 13.

In order to increase the efficiency with which the sample molecules reach the ionization section, as shown in FIG. 3, an inclined wall is provided inside the metal block 4b, and electrostatic spray is carried out obliquely toward the inclined wall, and ionization is performed. A gas 20 such as nitrogen may be flowed toward the part. It is desirable that the gas 20 is previously heated to room temperature or higher.

Further, in the structure shown in FIG. 2, if large droplets are generated by electrostatic spraying, the vaporization section 5 by the heating metal block 4b cannot completely vaporize, and corona discharge is generated by the needle electrode 7. Droplets may reach the generated ionization section 6 as they are. When the droplet reaches the portion where corona is generated, the needle electrode 7 and the ion introduction pore 9a
There is a possibility that the and may be short-circuited and the high-voltage power supply 8a or the like may be broken.

To prevent this, as shown in FIG.
The electrode 21a may be arranged so as to shield the end of the metal tube 3 and the ionization part 6 in which the corona discharge is generated by the needle-shaped electrode 7, and electrostatically spray toward the electrode 21a.
In this case, it is desirable that the electrode 21a is heated by the heater 22a in order to increase the vaporization efficiency of the droplets.
With the configuration shown in FIG. 4, only the gaseous molecules are carried to the ionization section 6 and ionized, so that a short circuit due to the droplets adhering to the needle electrode 7 is avoided. In FIG.
The shape of the electrode 21a is not limited to the plate shape, and may be a mesh. In order to increase the efficiency of the sample molecules reaching the ionization section 6, the gas 20 may be flown toward the ionization section 6 as in FIG.

Although the embodiments shown in FIGS. 2 to 4 show the constitution in which a heated metal block is used as a means for vaporizing the droplets, the vaporizing of the droplets may be performed by irradiating infrared rays. Good.

FIG. 5 shows an embodiment in which irradiation of infrared rays is used as the vaporizing means. The sample solution is electrostatically sprayed by the voltage applied between the metal tube 3 and the mesh 23a. It is desirable that the mesh 23a be heated. Droplets obtained by spraying are sent to the vaporization section 5. In the vaporization unit 5, the droplets are irradiated with infrared rays emitted from the heater 22b connected to the power source 24 to vaporize the droplets. In the case where the heater 22b is deteriorated by the droplets directly hitting the heater 22b, a glass tube 25 for protecting the heater 22b may be provided inside the heater 22b. In order to improve the efficiency of vaporization of droplets, the atomizing gas 1
It is desirable that the water vapor in 7 is removed. Also,
The atomizing gas 17 is preferably heated to room temperature or higher. The gaseous sample molecules obtained in the vaporization section 5 are
Corona discharge by the needle electrode 7 causes ionization in the ionization section 6 where hydronium ions and the like are generated.

With the structure shown in FIGS. 2 to 5, LC /
Although it is possible to use a mobile phase solvent containing a sparingly volatile salt in MS, when an extremely high concentration of salt is used or when analysis takes a long time, as shown in FIG.
Spraying may be performed in a direction perpendicular to the central axis of the ion introduction pore 9a. The sample solution introduced into the metal tube 3 is sprayed toward the facing electrode 21b. It is desirable that the electrode 21b is heated to the boiling point of the solution or higher.

The hardly volatile salt is deposited on this electrode 21b. Volatile sample molecules are vaporized and introduced into the ionization section 6 via the heated metal block 4b. In order to improve the efficiency of the sample molecules reaching the ionization section 6, an air supply port 26 is provided to allow the gas 20 such as dry nitrogen to pass through the ionization section 6.
You may run in the direction of. The gas 20 is preferably heated. Further, by providing an exhaust port 27 and exhausting gas from the exhaust port to the outside, an air flow in the direction of the ionization section 6 is generated from the portion where the solution is sprayed, and the sample molecules are efficiently introduced to the ionization section 6. Is also good.

Although the electrostatic spraying method is described as a method of spraying the solution in FIG. 6, when spraying in the direction perpendicular to the central axis of the ion introduction pore 9a, a spraying method other than electrostatic spraying, for example, heating is used. Spraying or ultrasonic spraying may be used.

Further, in the structure shown in FIG. 6, since the refractory salt is deposited on the electrode 21b, it is possible to easily perform maintenance by removing and cleaning only the electrode 21b.

FIG. 7 is a diagram showing a structure for spraying toward the mesh 23b instead of the counter electrode 21b shown in FIG. It is desirable that the mesh 23b is heated. A saucer 28 can be provided on the back of the mesh 23b, maintenance can be easily performed by replacing the saucer 28, and a solution accumulated in the saucer 28 can be collected and analyzed by a method other than mass spectrometry, such as fluorescence. It is possible to perform an analysis method by immunofluorescence or an immunological analysis method.

[0028]

According to the present invention, it is possible to use a mobile phase solvent containing a hardly volatile salt which has been difficult to use in conventional LC / MS. Therefore, the high separation capacity of LC can be fully utilized, the applicable range of LC / MS is expanded, and more substances can be analyzed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a mass spectrometer according to the present invention.

FIG. 2 is an explanatory diagram of an embodiment of the present invention.

FIG. 3 is a diagram showing an example in which a tip of a metal tube is provided in a vaporization section and a sample solution is directly sprayed toward a metal block.

FIG. 4 is a diagram showing an embodiment in which a shield plate for preventing large droplets from flying and reaching the ionization section is provided.

FIG. 5 is a diagram showing an example in which irradiation of infrared rays is used as a vaporization method for a vaporization section.

FIG. 6 is a diagram showing an example in which spraying is performed in a direction perpendicular to the central axis of ion introduction pores.

FIG. 7 is a diagram showing an embodiment in which a tray for collecting droplets is used.

FIG. 8 is a diagram showing a configuration of a conventional liquid chromatograph / mass spectrometer using an atmospheric pressure chemical ionization method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Piping, 2 ... Connector, 3 ... Metal tube, 4a, 4b ... Metal block, 5 ... Vaporization part, 6 ... Ionization part, 7 ... Needle-shaped electrode, 8a, 8b ... High voltage power supply, 9a, 9b ... Ion introduction thin Holes 10a, 10b ... Exhaust system, 11 ... Differential exhaust unit, 12
... high vacuum part, 13 ... mass spectrometric part, 14 ... liquid chromatograph, 15 ... electrostatic spraying part, 16 ... splitter, 17 ... spraying gas, 18 ... spraying auxiliary solution, 19 ... insulating tube, 20 ...
Gas, 21a, 21b ... Electrode, 22a, 22b ... Heater, 23a, 23b ... Mesh, 24 ... Power supply, 25 ... Glass tube, 26 ... Air supply port, 27 ... Exhaust port, 28 ... Saucepan.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takayuki Nabeshima 1-280, Higashi Koikeku, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Hideaki Koizumi 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi, Ltd. Central Research Center

Claims (22)

[Claims] 1. A liquid chromatograph for separating a mixed sample in a solution, and an atomizing means for atomizing a solution containing the sample obtained by the liquid chromatograph by electrostatic spraying. Vaporizing means for heating and vaporizing the droplets generated by the atomizing means, and chemical ionizing means for generating ions relating to the sample molecules by a chemical reaction with the gaseous sample molecules generated by the vaporizing means, A vacuum evacuation chamber having ion introduction pores for introducing ions generated by the chemical ionization means, and a mass spectrometric section for mass-analyzing the ions introduced from the ion introduction pores, Mass spectrometer. 2. A metal tube for introducing a solution containing a sample obtained by separation by the liquid chromatograph, an atomizing means for atomizing the sample introduced into the metal tube by electrostatic spraying, The mass spectrometer according to claim 1, further comprising means for introducing a gas for atomization around the metal tube for assisting atomization. 3. The mass spectrometer according to claim 1, further comprising means for introducing a spray auxiliary liquid around the metal tube. 4. The mass spectrometric analyzer according to claim 1, wherein the vaporizing means is a heated metal block surrounding a flow of droplets sprayed by the atomizing means. Total. 5. The vaporizing means comprises a heated metal block having a gas flow passage therein, and the tip of the metal pipe projects into the gas flow passage inside the metal block through an insulating means, The flow of the droplets sprayed by the atomizing means is arranged so as to collide with a part of the inner wall of the metal block forming the flow path. The mass spectrometer described. 6. The mass spectrometer according to claim 5, wherein the gas flowing through the gas passage is heated. 7. The mass spectrometer according to claim 1, wherein the vaporizing means is an infrared irradiation means. 8. The mass spectrometer according to claim 7, wherein the infrared irradiating means comprises a heater and a shield portion for preventing droplets from hitting the heater. 9. The mass spectrometer according to claim 1, wherein the chemical ionization means includes a needle electrode for generating a corona discharge. 10. The mass spectrometer according to claim 9, wherein the chemical ionization means generates a proton-added ion or a proton-desorbed ion of a sample molecule. 11. The mass spectrometric analyzer according to claim 1, further comprising a carrier gas flow generating means for carrying the atomized sample to the vaporizing means and the chemical ionizing means. Total. 12. The mass spectrometer according to claim 11, wherein the carrier gas flow generating means is gas supply from an air supply port. 13. The mass spectrometer according to claim 11, wherein the carrier gas is heated. 14. The mass spectrometer according to claim 11, wherein the carrier gas flow generating means is gas exhaust from an exhaust port. 15. The mass spectrometer according to claim 11, wherein the direction of the carrier gas flow intersects the direction of the flow of the liquid droplets sprayed by the atomizing means. 16. The mass spectrometer according to claim 1, wherein droplets are sprayed toward the mesh in the atomizing means. 17. The mass spectrometer according to claim 1, wherein the atomizing means heats the mesh onto which the droplets are sprayed. 18. The atomizing means further comprises means for collecting the droplets penetrating the mesh behind the mesh to which the droplets are sprayed.
17. The mass spectrometer according to claim 17. 19. A liquid chromatograph for separating a mixed sample in a solution, a metal tube into which the sample obtained by the liquid chromatograph is introduced, and a sample introduced into the metal tube Atomizing means for atomizing by electrospraying,
A means for introducing atomizing gas for assisting atomization around the metal tube, and a metal block surrounding the flow of droplets atomized by the atomizing means are provided to heat the droplets. A vaporization means for vaporizing, and a chemical ionization means for generating ions relating to the sample molecule by a chemical reaction with a gaseous sample molecule produced by the vaporizing means, comprising a needle electrode for generating a corona discharge, and A vacuum exhaust chamber provided with a carrier gas flow generating means for carrying the electrostatically sprayed sample to the vaporizing means and the chemical ionizing means, and an ion introducing pore for introducing the ions generated by the chemical ionizing means. And a mass spectrometer arranged in the evacuation chamber for mass spectrometric analysis of ions introduced from the ion introduction pores. 20. A shield portion is provided between the tip of the metal tube and the needle electrode to prevent droplets having a large particle diameter from flying and adhering to the needle electrode. The mass spectrometer according to claim 19. 21. The mass spectrometer according to claim 20, wherein the shield is made of a metal plate or a metal mesh. 22. The mass spectrometer according to claim 20, wherein the shield is heated.